Journal of Experimental Marine Biology and Ecology 253 2000 63–74
www.elsevier.nl locate jembe
Molecular and morphologic approaches to discrimination of variability patterns in chub mackerel, Scomber japonicus
a , b,c
a a
´ ´
´ ´
Marıa Ines Roldan , Ricardo G. Perrotta
, Martı Cortey , Carles Pla
a
` Laboratori d
’Ictiologia Genetica, Universitat de Girona, Campus Montilivi, E-17071 Girona, Spain
b
´ Instituto Nacional de Investigacion y Desarrollo Pesquero
INIDEP, Victoria Ocampo 1, 7600 Mar del Plata, Argentina
c
Departamento de Ciencias Marinas , Universidad Nacional de Mar del Plata, Mar del Plata, Argentina
Received 18 March 2000; received in revised form 18 May 2000; accepted 26 June 2000
Abstract
The systematic status and the evolutionary biology of chub mackerel Scomber japonicus in the South West Atlantic Ocean is confusing with an unknown degree of genetic differentiation and
reproductive isolation between units. Simultaneous genetic and morphologic analyses were made on 227 fish collected from two areas of the South West Atlantic Ocean and one from the
Mediterranean Sea. The genetic analysis was based on 36 protein-coding loci, 16 of which were variable. The morphologic analyses include six morphometric length measurements and a meristic
character. Correspondence between genetic and morphologic variability patterns indicates isolated Mediterranean and Southwest Atlantic subgroups of S
. japonicus and, less clearly, possible additional divergence in two regional stocks within the latter group. The most conservative
approach to management is to manage the stocks independently of one another.
2000 Elsevier Science B.V. All rights reserved.
Keywords : Chub mackerel; Scomber japonicus; Isozymes; Morphology; Population structure; Fisheries
1. Introduction
Chub mackerel Scomber japonicus is a widely exploited pelagic species with a total catch of 2,423,235 metric tons in 1997, taking it to fifth place in the total world nominal
catches FAO, 1997. S . japonicus has a cosmopolitan distribution including warm and
temperate waters of the Atlantic, Indian and Pacific Oceans and adjacent seas. As a
Corresponding author. Tel.: 134-972-418-961; fax: 134-972-418-277. ´
E-mail address : dbmrbxamba.udg.es M.I. Roldan.
0022-0981 00 – see front matter
2000 Elsevier Science B.V. All rights reserved. P I I : S 0 0 2 2 - 0 9 8 1 0 0 0 0 2 4 4 - 6
´ 64
M .I. Roldan et al. J. Exp. Mar. Biol. Ecol. 253 2000 63 –74
consequence of its broad distribution and the existence of oceanographical barriers, the species may be comprised of multiple disjunct populations. In the South West Atlantic
Ocean, many studies of local fishing grounds have highlighted different aspects of the ´
species’ biology Perrotta, 1992, 1993; Pajaro, 1993; Perrotta and Christiansen, 1993; Perrotta et al., 1997 and the fishery Perrotta and Pertierra, 1993; Perrotta et al., 1998b.
Two fishing stocks of chub mackerel north and south of latitude 398009S have been designated by their seasonal occurrence, observed behaviour and environmentally
induced morphometric characteristics. These stocks are operational units used in fishery management, with small purse-seining boats Lampara net operating in the Mar del
´ Plata area and large trawling boats in El Rincon Perrotta et al., 1998a.
Allozyme data have clarified intraspecific relationships in two mackerel species Scomber scombrus, Jamieson and Smith, 1987, and references therein; Scomberomorus
cavalla, Johnson et al., 1994. Nevertheless, in spite of the interest to fisheries, no study has been published on S
. japonicus. This paper examines the population structure of chub mackerel in the South West
Atlantic Ocean based on genetic variation at 16 protein-coding loci and seven morphologic characters. Moreover, we summarize current information on growth,
migration and spawning time and propose a possible mechanism to explain the observed patterns with regard to the water circulation of the area. We also compare levels of
genetic diversity and differentiation with the North Atlantic population Mediterranean Sea.
2. Methods
